OCCTH 585 NEURO
Information flows through neurons from ____ to ____ in the neuron - Answer-
dendrite; axon
_____ bring a cell to threshold while _____ bring a cell further from threshold -
Answer- EPSPs; IPSPs
What 3 main things is neuroplasticity capable of? - Answer- - changing the properties
of neurotransmission
- changes in cell properties
- structural/ anatomical changes of cells
How does neuroplasticity change the properties of neurotransmission? (2) - Answer-
- change in transmitter size
- change in PSP size or shape
How does neuroplasticity change the properties of cells? (3) - Answer- - size and
shape
- electrical properties (resistance)
- "leakiness" of membrane
What is unmasking? - Answer- when an injury, event, or illness eliminates the inputs
that a neuron most commonly responds to (i.e. blue --> blue region of brain), the
neuron will become more responsive to the other inputs on the neuron (i.e. yellow -->
yellow region of brain) and that new representation will increase; is immediate,
involves exposure of pre-existing synapses, and creates functional changes in the
cell
What is dendritic pruning? - Answer- when dendrites with no active synapses are
retracted to reduce the amount of resources wasted to keep those useless dendrites
alive; changes cellular properties (size and shape) and creates as 'loss of real
estate', decreases energy expenditure
What is collateral sprouting? - Answer- when neurons sprout new synapses on bare
dendrites (either after pruning of dead synapses or less used working ones) leading
the cell to become more responsive to those new inputs
What can lead to collateral sprouting? - Answer- more stimulation; higher
representation is driven by high rates of APs
What are the 6 mechanisms of collateral sprouting? - Answer- - growth of new bits
- requires time
- fill vacancy OR push less used synapses out of the way
- activity dependent
- produces functional changes
,Do neurons have to be close to the "free real estate" in order to make new
collaterals? Do they need to already be involved with it? - Answer- no, the closest
ones will usually get there first, but the axons can grow out 1-2cm to form a
connection (any further = stuff in the way, would take too long and die); no
What signals to other neurons that there is space to form new collaterals and guides
them to it? - Answer- neurotrophin (released by dendritic spines through APs)
What are chemoattractants? - Answer- neurotrophins and other chemical signals that
signal to a neuron to grow their collaterals in that direction
What are chemorepellants? - Answer- chemical signals that signal to a neuron to
grow their collaterals away from that direction
What structures release chemoattractants and chemorepellants? - Answer- guide
cells
What is a growth cone? - Answer- a specialized structure at the end of the axon that
has filopodia that branch out in multiple directions to look for chemoattractive and
chemorepellant signals
Are neurons always responsive to guidance molecules? - Answer- no, they are time-
locked based on the developmental clock of the embryo; some guidance molecules
can be both a chemoattractant and a chemorepellant depending on the embryo's
current stage of development
A large chemorepellant signal can lead to ____ ____ ____; exposure can also signal
____________________ - Answer- growth cone collapse; growth of filipodia off
growth of different spots of the neuron
Where are new neurons produced? (3) - Answer- - subventricular zone (olfactory)
- dentrate gyrus of hippocampus (memory)
- Cerebral cortex
What are neurons and neurogenesis' roles in learning and memory? (3) - Answer- -
undergo synaptic plasticity to retain memory
- can become "locked" for longterm memory
- can be replaced to allow new learning
___-___% of neurons in the hippocampus are replaced _____ - Answer- 20-25%;
monthly
What types of cells can stem cells turn into? - Answer- - oligodendrocyte
- astrocyte
- neuron
What things determine the type of cell that stem cells differentiate into? (2) - Answer-
- level of hormones (estrogen increases, glucocorticoids decrease)
- environmental factors (in CNS, most often are astrocytes; neurons survive longer in
enriched environment)
, What barriers do we face in attempting to direct stem cells to produce neurons
needed to repair injuries? (6) - Answer- - nervous system laid out first in embryos;
difficult to build around everything else in adults
- difficult to replicate static environment needed for neurons to be generated
- difficult to get cells to go to the repair location (no guide cells)
- migration and differentiation occur simultaneously
- don't integrate well and will eventually die
- if stem cells are poorly activated, a tumor can be created
What is different about mature neurons vs embryonic neurons? - Answer- - many
cues no longer produced
- cells, especially neurons, are no longer responsive
- guide cells no longer exist
What 7 things occur in the nervous system following an injury? - Answer- - terminal
degeneration
- Wallerian degeneration
- myelin debris
- macrophage infiltration
- chromatolysis
- retraction of synaptic terminals
- degeneration
ALL HAPPENS SIMULTANEOUSLY
What is Wallerian degeneration? - Answer- axon distal to injury degenerates
because it is cut off from the cell body
Why is myelin debris created? - Answer- the part of the axon it is on degenerated, so
it is no longer needed
Why does macrophage infiltration occur? - Answer- to clean up the myelin debris
What is chromatolysis? - Answer- dispersion of Nissl substance and swelling of the
cell body due to high rate of protein production in order to attempt to repair in the
injured neuron
What is retrograde degeneration? - Answer- loss of the proximal portion to the lesion
after an injury to the axon
What is anterograde degeneration? - Answer- loss of the distal portion to the lesion
after an injury to the axon
What is transneuronal degeneration? When does this occur? - Answer- loss of
neurons that synapse on the damaged neuron; only occurs if a cell loses all of its
inputs
What can occur after neural degeneration? - Answer- collateral sprouting
Information flows through neurons from ____ to ____ in the neuron - Answer-
dendrite; axon
_____ bring a cell to threshold while _____ bring a cell further from threshold -
Answer- EPSPs; IPSPs
What 3 main things is neuroplasticity capable of? - Answer- - changing the properties
of neurotransmission
- changes in cell properties
- structural/ anatomical changes of cells
How does neuroplasticity change the properties of neurotransmission? (2) - Answer-
- change in transmitter size
- change in PSP size or shape
How does neuroplasticity change the properties of cells? (3) - Answer- - size and
shape
- electrical properties (resistance)
- "leakiness" of membrane
What is unmasking? - Answer- when an injury, event, or illness eliminates the inputs
that a neuron most commonly responds to (i.e. blue --> blue region of brain), the
neuron will become more responsive to the other inputs on the neuron (i.e. yellow -->
yellow region of brain) and that new representation will increase; is immediate,
involves exposure of pre-existing synapses, and creates functional changes in the
cell
What is dendritic pruning? - Answer- when dendrites with no active synapses are
retracted to reduce the amount of resources wasted to keep those useless dendrites
alive; changes cellular properties (size and shape) and creates as 'loss of real
estate', decreases energy expenditure
What is collateral sprouting? - Answer- when neurons sprout new synapses on bare
dendrites (either after pruning of dead synapses or less used working ones) leading
the cell to become more responsive to those new inputs
What can lead to collateral sprouting? - Answer- more stimulation; higher
representation is driven by high rates of APs
What are the 6 mechanisms of collateral sprouting? - Answer- - growth of new bits
- requires time
- fill vacancy OR push less used synapses out of the way
- activity dependent
- produces functional changes
,Do neurons have to be close to the "free real estate" in order to make new
collaterals? Do they need to already be involved with it? - Answer- no, the closest
ones will usually get there first, but the axons can grow out 1-2cm to form a
connection (any further = stuff in the way, would take too long and die); no
What signals to other neurons that there is space to form new collaterals and guides
them to it? - Answer- neurotrophin (released by dendritic spines through APs)
What are chemoattractants? - Answer- neurotrophins and other chemical signals that
signal to a neuron to grow their collaterals in that direction
What are chemorepellants? - Answer- chemical signals that signal to a neuron to
grow their collaterals away from that direction
What structures release chemoattractants and chemorepellants? - Answer- guide
cells
What is a growth cone? - Answer- a specialized structure at the end of the axon that
has filopodia that branch out in multiple directions to look for chemoattractive and
chemorepellant signals
Are neurons always responsive to guidance molecules? - Answer- no, they are time-
locked based on the developmental clock of the embryo; some guidance molecules
can be both a chemoattractant and a chemorepellant depending on the embryo's
current stage of development
A large chemorepellant signal can lead to ____ ____ ____; exposure can also signal
____________________ - Answer- growth cone collapse; growth of filipodia off
growth of different spots of the neuron
Where are new neurons produced? (3) - Answer- - subventricular zone (olfactory)
- dentrate gyrus of hippocampus (memory)
- Cerebral cortex
What are neurons and neurogenesis' roles in learning and memory? (3) - Answer- -
undergo synaptic plasticity to retain memory
- can become "locked" for longterm memory
- can be replaced to allow new learning
___-___% of neurons in the hippocampus are replaced _____ - Answer- 20-25%;
monthly
What types of cells can stem cells turn into? - Answer- - oligodendrocyte
- astrocyte
- neuron
What things determine the type of cell that stem cells differentiate into? (2) - Answer-
- level of hormones (estrogen increases, glucocorticoids decrease)
- environmental factors (in CNS, most often are astrocytes; neurons survive longer in
enriched environment)
, What barriers do we face in attempting to direct stem cells to produce neurons
needed to repair injuries? (6) - Answer- - nervous system laid out first in embryos;
difficult to build around everything else in adults
- difficult to replicate static environment needed for neurons to be generated
- difficult to get cells to go to the repair location (no guide cells)
- migration and differentiation occur simultaneously
- don't integrate well and will eventually die
- if stem cells are poorly activated, a tumor can be created
What is different about mature neurons vs embryonic neurons? - Answer- - many
cues no longer produced
- cells, especially neurons, are no longer responsive
- guide cells no longer exist
What 7 things occur in the nervous system following an injury? - Answer- - terminal
degeneration
- Wallerian degeneration
- myelin debris
- macrophage infiltration
- chromatolysis
- retraction of synaptic terminals
- degeneration
ALL HAPPENS SIMULTANEOUSLY
What is Wallerian degeneration? - Answer- axon distal to injury degenerates
because it is cut off from the cell body
Why is myelin debris created? - Answer- the part of the axon it is on degenerated, so
it is no longer needed
Why does macrophage infiltration occur? - Answer- to clean up the myelin debris
What is chromatolysis? - Answer- dispersion of Nissl substance and swelling of the
cell body due to high rate of protein production in order to attempt to repair in the
injured neuron
What is retrograde degeneration? - Answer- loss of the proximal portion to the lesion
after an injury to the axon
What is anterograde degeneration? - Answer- loss of the distal portion to the lesion
after an injury to the axon
What is transneuronal degeneration? When does this occur? - Answer- loss of
neurons that synapse on the damaged neuron; only occurs if a cell loses all of its
inputs
What can occur after neural degeneration? - Answer- collateral sprouting
